Power Transmission Fluid Compositions and Preparation Thereof

ABSTRACT

A power transmission fluid composition meeting required specifications of manufactures is provided. The power transmission fluid composition contains a sufficient amount of a Pour Point Reducing Blend Component for the power transmission fluid to have a Brookfield viscosity at −40° C. of less than or equal to 16,000 cP. The Pour Point Reducing Blend Component is selected from an isomerized Fischer-Tropsch derived bottoms product, a bottoms product prepared from an isomerized highly waxy mineral oil, and mixtures thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 USC 119 of Provisional Application 61/015265 filed Dec. 20, 2007. This application claims priority to and benefits from the foregoing, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates generally to power transmission fluids, and more specifically to power transmission compositions comprising Pour Point Reducing Blend Component materials as a pour point depressant.

BACKGROUND

Power transmission fluid is defined as any lubricant used in contact with gears involved in the transmission of mechanical energy in devices including, but not be limited to, automatic transmissions, manual transmissions, continuously variable transmissions, automated manual transmissions, transfer cases, axles, differentials, and combinations thereof as used in mobile applications, i.e., automotive and commercial vehicle services. Power transmission fluid can also be used for stationary gearing applications. Power transmission fluid properties are typically adjusted to meet automotive/commercial vehicle manufacturers' specific requirements, guaranteeing safe power transfer and shift performance at low and high sliding speeds. Basic property requirements include high thermal and oxidation resistance, low temperature fluidity, high compatibility, foam control, corrosion control, anti-wear properties, and friction properties at high sliding speeds. To meet certain specifications, power transmission fluids such as automatic transmission fluids (ATF's) preferably have a kinematic viscosity (cSt) between 30-60 at 40° C., and between 4 to 10 at 100° C.; Brookfield viscosity of below 20000 mPas at −40° C., flash points (COC) between 150-220° C.; and pour point between −36 to −48° C.

Power transmission fluid compositions in the prior art typically employ a Group I, II, III, a synthetic PAO (for poly α-olefin) or mixtures thereof as a base oil stock. The groups are broad categories of base stocks developed by the American Petroleum Institute (API) for the purpose of creating guidelines for base oils.

The Fischer-Tropsch synthesis products can be obtained by well-known processes such as, for example, the commercial SASOL® Slurry Phase Fischer-Tropsch technology, the commercial SHELL® Middle Distillate Synthesis (SMDS) Process, or by the non-commercial EXXON® Advanced Gas Conversion (AGC-21) process. Details of these processes and others are described in, for example, EP-A-776959, EP-A-668342; U.S. Pat. Nos. 4,943,672, 5,059,299, 5,733,839, and RE39073 ; and US Published Application No. 2005/0227866, WO-A-9934917, WO-A-9920720 and WO-A-05107935. The Fischer-Tropsch synthesis product usually comprises hydrocarbons having 1 to 100, or even more than 100 carbon atoms, and typically includes paraffins, olefins and oxygenated products. Fischer Tropsch is a viable process to generate clean alternative hydrocarbon products. In the process of making Fischer Tropsch base oil, an intermediate feed or product may be fractionated by atmospheric or vacuum distillation. In cases where a broad boiling hydroisomerized base oil is fractionated, the bottoms material collected from the vacuum distillation column comprises a mixture of high boiling hydrocarbons.

There is a need for power transmission fluids compositions meeting required specifications, utilizing less common hydrocarbon products—including the “bottoms” material or Pour Point Reducing Blend Component materials.

SUMMARY OF THE INVENTION

In one embodiment, there is provided a power transmission fluid composition comprising (a) a base oil; (b) at least one of an additive package, a friction modifier, a dispersant, an antioxidant, an anti-foamant, an antiwear agent, an antifoam agent, a metal-based detergent, and a viscosity index improver; and (c) a sufficient amount of a Pour Point Reducing Blend Component for the power transmission fluid to have a Brookfield viscosity at −40° C. of less than or equal to 16,000 cP. In one embodiment, this sufficient amount of a Pour Point Reducing Blend Component for the power transmission fluid to have a Brookfield viscosity at −40° C. of less than or equal to 16,000 cP is between 0.5 to 15 wt. %.

In another aspect, there is provided a method to improve the Brookfield viscosity characteristic of a power transmission fluid including the step of mixing: (a) a base oil; (b) at least one of an additive package, a friction modifier, a dispersant, an antioxidant, an anti-foamant, an antiwear agent, an antifoam agent, a metal-based detergent, and a viscosity index improver; with (c) a sufficient amount of a Pour Point Reducing Blend Component for the power transmission fluid to have a Brookfield viscosity at −40° C. of less than or equal to 16,000 cP.

DETAILED DESCRIPTION

The following terms will be used throughout the specification and will have the following meanings unless otherwise indicated.

“Power transmission fluid” may be used interchangeably with “automatic transmission fluid,” or “ATF,” referring to a composition to lubricate gears involved in the transmission of mechanical energy of mobile applications as well as stationary gearing applications.

“Fischer-Tropsch derived” means that the product, fraction, or feed originates from or is produced at some stage by a Fischer-Tropsch process. As used herein, “Fischer-Tropsch base oil” may be used interchangeably with “FT base oil,” “FTBO,” “GTL base oil” (GTL: gas-to-liquid), or “Fischer-Tropsch derived base oil.”

As used herein, “isomerized base oil” refers to a base oil made by isomerization of a waxy feed.

As used herein, a “waxy feed” comprises at least 40 wt % n-paraffins. In one embodiment, the waxy feed comprises greater than 50 wt % n-paraffins. In another embodiment, greater than 75 wt % n-paraffins. In one embodiment, the waxy feed also has very low levels of nitrogen and sulphur, e.g., less than 25 ppm total combined nitrogen and sulfur, or in other embodiments less than 20 ppm. Examples of waxy feeds include slack waxes, deoiled slack waxes, refined foots oils, waxy lubricant raffinates, n-paraffin waxes, NAO waxes, waxes produced in chemical plant processes, deoiled petroleum derived waxes, microcrystalline waxes, Fischer-Tropsch waxes, and mixtures thereof. In one embodiment, the waxy feeds have a pour point of greater than 50° C. In another embodiment, greater than 60° C.

As used herein, “Pour Point Reducing Blend Component” refers to an isomerized waxy product with relatively high molecular weights and a specified degree of alkyl branching in the molecule, such that it reduces the pour point of lubricating base oil blends containing it. Examples of a Pour Point Reducing Blend Component are disclosed in U.S. Pat. Nos. 6,150,577 and 7,053,254, and Patent Publication No. US 2005-0247600 A1. A Pour Point Reducing Blend Component can be: 1) an isomerized Fischer-Tropsch derived bottoms product; 2) a bottoms product prepared from an isomerized highly waxy mineral oil, or 3) an isomerized oil having a kinematic viscosity at 100° C. of at least about 8 mm²/s made from polyethylene plastic.

As used herein, the “10 percent point” of the boiling range of a Pour Point Reducing Blend Component refers to the temperature at which 10 weight percent of the hydrocarbons present within that cut will vaporize at atmospheric pressure. Similarly, the 90 percent point of the respective boiling ranges refers to the temperature at which 90 weight percent of the hydrocarbons present within that cut will vaporize at atmospheric pressure. For samples having a boiling range above 1000° F. (538° C.), the boiling range can be measured using the standard analytical method D-6352-04 or its equivalent. For samples having a boiling range below 1000° F. (538° C.), the boiling range distributions in this disclosure can be measured using the standard analytical method D-2887-06 or its equivalent. It will be noted that only the 10 percent point of the respective boiling range is used when referring to the Pour Point Reducing Blend Component that is a vacuum distillation bottoms product, since it is derived from a bottoms fraction which makes the 90 percent point or upper boiling limit irrelevant.

“Kinematic viscosity” is a measurement in mm²/s of the resistance to flow of a fluid under gravity, determined by ASTM D445-06.

“Viscosity index” (VI) is an empirical, unit-less number indicating the effect of temperature change on the kinematic viscosity of the oil. The higher the VI of an oil, the lower its tendency to change viscosity with temperature. Viscosity index is measured according to ASTM D 2270-04.

Cold-cranking simulator apparent viscosity (CCS VIS) is a measurement in millipascal seconds, mPa·s to measure the viscometric properties of lubricating base oils under low temperature and low shear. CCS VIS is determined by ASTM D 5293-04.

The boiling range distribution of base oil, by wt %, is determined by simulated distillation (SIMDIS) according to ASTM D 6352-04, “Boiling Range Distribution of Petroleum Distillates in Boiling Range from 174 to 700° C. by Gas Chromatography.”

“Noack volatility” is defined as the mass of oil, expressed in weight %, which is lost when the oil is heated at 250° C. with a constant flow of air drawn through it for 60 min., measured according to ASTM D5800-05, Procedure B.

Brookfield viscosity is used to determine the internal fluid-friction of a lubricant during cold temperature operation, which can be measured by ASTM D 2983-04.

“Pour point” is a measurement of the temperature at which a sample of base oil will begin to flow under certain carefully controlled conditions, which can be determined as described in ASTM D 5950-02.

“Auto ignition temperature” is the temperature at which a fluid will ignite spontaneously in contact with air, which can be determined according to ASTM 659-78.

“Ln” refers to natural logarithm with base “e.”

“Traction coefficient” is an indicator of intrinsic lubricant properties, expressed as the dimensionless ratio of the friction force F and the normal force N, where friction is the mechanical force which resists movement or hinders movement between sliding or rolling surfaces. Traction coefficient can be measured with an MTM Traction Measurement System from PCS Instruments, Ltd., configured with a polished 19 mm diameter ball (SAE AISI 52100 steel) angled at 220 to a flat 46 mm diameter polished disk (SAE AISI 52100 steel). The steel ball and disk are independently measured at an average rolling speed of 3 meters per second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. The roll ratio is defined as the difference in sliding speed between the ball and disk divided by the mean speed of the ball and disk, i.e. roll ratio=(Speed1−Speed2)/((Speed1+Speed2)−/2).

As used herein, “consecutive numbers of carbon atoms” means that the base oil has a distribution of hydrocarbon molecules over a range of carbon numbers, with every number of carbon numbers in-between. For example, the base oil may have hydrocarbon molecules ranging from C22 to C36 or from C30 to C60 with every carbon number in-between. The hydrocarbon molecules of the base oil differ from each other by consecutive numbers of carbon atoms, as a consequence of the waxy feed also having consecutive numbers of carbon atoms. For example, in the Fischer-Tropsch hydrocarbon synthesis reaction, the source of carbon atoms is CO and the hydrocarbon molecules are built up one carbon atom at a time. Petroleum-derived waxy feeds have consecutive numbers of carbon atoms. In contrast to an oil based on poly-alpha-olefin (“PAO”), the molecules of an isomerized base oil have a more linear structure, comprising a relatively long backbone with short branches. The classic textbook description of a PAO is a star-shaped molecule, and in particular tridecane, which is illustrated as three decane molecules attached at a central point. While a star-shaped molecule is theoretical, nevertheless PAO molecules have fewer and longer branches that the hydrocarbon molecules that make up the isomerized base oil disclosed herein.

“Molecules with cycloparaffinic functionality” mean any molecule that is, or contains as one or more substituents, a monocyclic or a fused multicyclic saturated hydrocarbon group.

“Molecules with monocycloparaffinic functionality” mean any molecule that is a monocyclic saturated hydrocarbon group of three to seven ring carbons or any molecule that is substituted with a single monocyclic saturated hydrocarbon group of three to seven ring carbons.

“Molecules with multicycloparaffinic functionality” mean any molecule that is a fused multicyclic saturated hydrocarbon ring group of two or more fused rings, any molecule that is substituted with one or more fused multicyclic saturated hydrocarbon ring groups of two or more fused rings, or any molecule that is substituted with more than one monocyclic saturated hydrocarbon group of three to seven ring carbons.

Molecules with cycloparaffinic functionality, molecules with monocycloparaffinic functionality, and molecules with multicycloparaffinic functionality are reported as weight percent and are determined by a combination of Field Ionization Mass Spectroscopy (FIMS), HPLC-UV for aromatics, and Proton NMR for olefins, further fully described herein.

Oxidator BN measures the response of a lubricating oil in a simulated application. High values, or long times to adsorb one liter of oxygen, indicate good stability. Oxidator BN can be measured via a Domte-type oxygen absorption apparatus (R. W. Dornte “Oxidation of White Oils,” Industrial and Engineering Chemistry, Vol. 28, page 26, 1936), under 1 atmosphere of pure oxygen at 340° F., time to absorb 1000 ml of O₂ by 100 g. of oil is reported. In the Oxidator BN test, 0.8 ml of catalyst is used per 100 grams of oil. The catalyst is a mixture of soluble metal-naphthenates simulating the average metal analysis of used crankcase oil. The additive package is 80 millimoles of zinc bispolypropylenephenyldithiophosphate per 100 grams of oil.

Molecular characterizations can be performed by methods known in the art, including Field Ionization Mass Spectroscopy (FIMS) and n-d-M analysis (ASTM D 3238-95 (Re-approved 2005) with normalization). In FIMS, the base oil is characterized as alkanes and molecules with different numbers of unsaturations. The molecules with different numbers of unsaturations may be comprised of cycloparaffins, olefins, and aromatics. If aromatics are present in significant amount, they would be identified as 4-unsaturations. When olefins are present in significant amounts, they would be identified as 1-unsaturations. The total of the 1-unsaturations, 2-unsaturations, 3-unsaturations, 4-unsaturations, 5-unsaturations, and 6-unsaturations from the FIMS analysis, minus the wt % olefins by proton NMR, and minus the wt % aromatics by HPLC-UV is the total weight percent of molecules with cycloparaffinic functionality. If the aromatics content was not measured, it was assumed to be less than 0.1 wt % and not included in the calculation for total weight percent of molecules with cycloparaffinic functionality. The total weight percent of molecules with cycloparaffinic functionality is the sum of the weight percent of molecules with monocyclopraffinic functionality and the weight percent of molecules with multicycloparaffinic functionality.

Molecular weights are determined by ASTM D2503-92(Reapproved 2002). The method uses thermoelectric measurement of vapour pressure (VPO). In circumstances where there is insufficient sample volume, an alternative method of ASTM D2502-04 may be used; and where this has been used it is indicated.

Density is determined by ASTM D4052-96 (Reapproved 2002). The sample is introduced into an oscillating sample tube and the change in oscillating frequency caused by the change in the mass of the tube is used in conjunction with calibration data to determine the density of the sample.

Weight percent olefins can be determined by proton-NMR according to the steps specified herein. In most tests, the olefins are conventional olefins, i.e. a distributed mixture of those olefin types having hydrogens attached to the double bond carbons such as: alpha, vinylidene, cis, trans, and tri-substituted, with a detectable allylic to olefin integral ratio between 1 and 2.5. When this ratio exceeds 3, it indicates a higher percentage of tri or tetra substituted olefins being present, thus other assumptions known in the analytical art can be made to calculate the number of double bonds in the sample. A solution of 5-10% of the sample in deuterochloroform can be prepared, giving a normal proton spectrum of at least 12 ppm spectral width. Tetramethylsilane (TMS) can be used as an internal reference standard. The instrument used to acquire the spectrum and reference the chemical shift has sufficient gain range to acquire a signal without overloading the receiver/ADC, with a minimum signal digitization dynamic range of at least 65,000 when a 30 degree pulse is applied. The intensities of the proton signals in the region of 0.5-1.9 ppm (methyl, methylene and methine groups), 1.9-2.2 ppm (allylic) and between 6.0-4.5 ppm (olefin) are measured. Using the average molecular weight (estimated by vapor pressure osmometry by ASTM D 2503-92[re-approved 2002]) of each distillate range paraffin feed, the following can be calculated: (1) the average molecular formula of the saturated hydrocarbons; (2) the average molecular formula of the olefins; (3) the total integral intensity (i.e. the sum of all the integral intensities); (4) the integral intensity per sample hydrogen (i.e. the total integral intensity divided by the number of hydrogens in the formula; (5) the number of olefin hydrogens (i.e. the olefin integral divided by the integral per hydrogen); (6) the number of double bonds (i.e. the olefin hydrogen multiplied by the hydrogens in the olefin formula divided by 2); and (7) the weight percent olefins (i.e. 100 multiplied by the number of double bonds multiplied by the number of hydrogens in a typical olefin molecule divided by the number of hydrogens in a typical distillate range paraffin feed molecule). This Proton NMR procedure to calculate the olefin content of the sample works best when the olefin content is low, e.g., less than about 15 weight percent.

Weight percent aromatics in one embodiment can be measured by HPLC-UV. In one embodiment, the test is conducted using a Hewlett Packard 1050 Series Quaternary Gradient High Performance Liquid Chromatography (HPLC) system, coupled with a HP 1050 Diode-Array UV-Vis detector interfaced to an HP Chem-station. Identification of the individual aromatic classes in the highly saturated base oil can be made on the basis of the UV spectral pattern and the elution time. The amino column used for this analysis differentiates aromatic molecules largely on the basis of their ring-number (or double-bond number). Thus, the single ring aromatic containing molecules elute first, followed by the polycyclic aromatics in order of increasing double bond number per molecule. For aromatics with similar double bond character, those with only alkyl substitution on the ring elute sooner than those with naphthenic substitution. Unequivocal identification of the various base oil aromatic hydrocarbons from their UV absorbance spectra can be accomplished recognizing that their peak electronic transitions are all red-shifted relative to the pure model compound analogs to a degree dependent on the amount of alkyl and naphthenic substitution on the ring system. Quantification of the eluting aromatic compounds can be made by integrating chromatograms made from wavelengths optimized for each general class of compounds over the appropriate retention time window for that aromatic. Retention time window limits for each aromatic class can be determined by manually evaluating the individual absorbance spectra of eluting compounds at different times and assigning them to the appropriate aromatic class based on their qualitative similarity to model compound absorption spectra.

Weight percent aromatic carbon (“Ca”), weight percent naphthenic carbon (“Cn”) and weight percent paraffinic carbon (“Cp”) in one embodiment can be measured by ASTM D3238-95 (Reapproved 2005) with normalization. ASTM D3238-95 (Reapproved 2005) is the Standard Test Method for Calculation of Carbon Distribution and Structural Group Analysis of Petroleum Oils by the n-d-M Method. This method is for “olefin free” feedstocks which are assumed in this application to mean that that olefin content is 2 wt % or less. The normalization process consists of the following: A) If the Ca value is less than zero, Ca is set to zero, and Cn and Cp are increased proportionally so that the sum is 100%. B) If the Cn value is less than zero, Cn is set to zero, and Ca and Cp are increased proportionally so that the sum is 100%; and C) If both Cn and Ca are less than zero, Cn and Ca are set to zero, and Cp is set to 100%.

HPLC-UV Calibration. In one embodiment, HPLC-UV can be used for identifying classes of aromatic compounds even at very low levels, e.g., multi-ring aromatics typically absorb 10 to 200 times more strongly than single-ring aromatics. Alkyl-substitution affects absorption by 20%. Integration limits for the co-eluting 1-ring and 2-ring aromatics at 272nm can be made by the perpendicular drop method. Wavelength dependent response factors for each general aromatic class can be first determined by constructing Beer's Law plots from pure model compound mixtures based on the nearest spectral peak absorbances to the substituted aromatic analogs. Weight percent concentrations of aromatics can be calculated by assuming that the average molecular weight for each aromatic class was approximately equal to the average molecular weight for the whole base oil sample.

NMR analysis. In one embodiment, the weight percent of all molecules with at least one aromatic function in the purified mono-aromatic standard can be confirmed via long-duration carbon 13 NMR analysis. The NMR results can be translated from % aromatic carbon to % aromatic molecules (to be consistent with HPLC-UV and D 2007) knowing that 95-99% of the aromatics in highly saturated base oils are single-ring aromatics. In another test to accurately measure low levels of all molecules with at least one aromatic function by NMR, the standard D 5292-99 (Reapproved 2004) method can be modified to give a minimum carbon sensitivity of 500:1 (by ASTM standard practice E 386) with a 15-hour duration run on a 400-500 MHz NMR with a 10-12 mm Nalorac probe. Acorn PC integration software can be used to define the shape of the baseline and consistently integrate.

Extent of branching refers to the number of alkyl branches in hydrocarbons. Branching and branching position can be determined using carbon-13 (¹³C) NMR according to the following nine-step process: 1) Identify the CH branch centers and the CH₃ branch termination points using the DEPT Pulse sequence (Doddrell, D. T.; D. T. Pegg; M. R. Bendall, Journal of Magnetic Resonance 1982, 48, 323ff.). 2) Verify the absence of carbons initiating multiple branches (quaternary carbons) using the APT pulse sequence (Patt, S. L.; J. N. Shoolery, Journal of Magnetic Resonance 1982, 46, 535ff.). 3) Assign the various branch carbon resonances to specific branch positions and lengths using tabulated and calculated values known in the art (Lindeman, L. P., Journal of Qualitative Analytical Chemistry 43, 1971 1245ff; Netzel, D. A., et.al., Fuel, 60, 1981, 307ff). 4) Estimate relative branching density at different carbon positions by comparing the integrated intensity of the specific carbon of the methyl/alkyl group to the intensity of a single carbon (which is equal to total integral/number of carbons per molecule in the mixture). For the 2-methyl branch, where both the terminal and the branch methyl occur at the same resonance position, the intensity is divided by two before estimating the branching density. If the 4-methyl branch fraction is calculated and tabulated, its contribution to the 4+methyls is subtracted to avoid double counting. 5) Calculate the average carbon number. The average carbon number is determined by dividing the molecular weight of the sample by 14 (the formula weight of CH₂). 6) The number of branches per molecule is the sum of the branches found in step 4. 7) The number of alkyl branches per 100 carbon atoms is calculated from the number of branches per molecule (step 6) times 100/average carbon number. 8) Estimate Branching Index (BI) by ¹H NMR Analysis, which is presented as percentage of methyl hydrogen (chemical shift range 0.6-1.05 ppm) among total hydrogen as estimated by NMR in the liquid hydrocarbon composition. 9) Estimate Branching proximity (BP) by ¹³C NMR, which is presented as percentage of recurring methylene carbons—which are four or more carbons away from the end group or a branch (represented by a NMR signal at 29.9 ppm) among total carbons as estimated by NMR in the liquid hydrocarbon composition. The measurements can be performed using any Fourier Transform NMR spectrometer, e.g., one having a magnet of 7.0 T or greater. After verification by Mass Spectrometry, UV or an NMR survey that aromatic carbons are absent, the spectral width for the ¹³C NMR studies can be limited to the saturated carbon region, 0-80 ppm vs. TMS (tetramethylsilane). Solutions of 25-50 wt. % in chloroform-dl are excited by 30 degrees pulses followed by a 1.3 seconds (sec.) acquisition time. In order to minimize non-uniform intensity data, the broadband proton inverse-gated decoupling is used during a 6 sec. delay prior to the excitation pulse and on during acquisition. Samples are doped with 0.03 to 0.05 M Cr (acac)₃ (tris (acetylacetonato)-chromium (III)) as a relaxation agent to ensure full intensities are observed. The DEPT and APT sequences can be carried out according to literature descriptions with minor deviations described in the Varian or Bruker operating manuals. DEPT is Distortionless Enhancement by Polarization Transfer. The DEPT 45 sequence gives a signal all carbons bonded to protons. DEPT 90 shows CH carbons only. DEPT 135 shows CH and CH₃ up and CH₂ 180 degrees out of phase (down). APT is attached proton test, known in the art. It allows all carbons to be seen, but if CH and CH₃ are up, then quaternaries and CH₂ are down. The branching properties of the sample can be determined by ¹³C NMR using the assumption in the calculations that the entire sample was iso-paraffinic. The unsaturates content may be measured using Field Ionization Mass Spectroscopy (FIMS).

In one embodiment, the power transmission fluid composition comprises optional additives in a matrix of base oil or base oil blends comprising a sufficient amount of at least a Pour Point Reducing Blend Component as a pour point depressant.

Base Oil Component: Besides the Pour Point Reducing Blend Component and optional additives, the power transmission fluid contains a major amount of at least a base oil (or blends thereof) in an amount ranging from 70 to 90 wt. % in one embodiment, from 75 to 80 wt. % in a second embodiment, and from 75 to 85 wt. % in a third embodiment. In one embodiment, the base oil has a viscosity 100° C. of 2 to 15 cSt. In another embodiment, the base oil has a viscosity of less than 10 cSt at 100° C. In a third embodiment, a viscosity of less than 5 cSt at 100° C. Base oils suitable for use in formulating transmission fluid compositions are selected from any of the synthetic or natural oils or mixtures thereof, e.g., any of the base oils in Groups I-V as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines.

Examples of natural oils include animal oils and vegetable oils (e.g., castor oil, lard oil) and mineral lubricating oils such as liquid petroleum oils and solvent treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinicnaphthenic types. Oils derived from coal or shale are also suitable. Further, oils derived from a gas-to-liquid process are also suitable.

In one embodiment, synthetic oils for use include hydrocarbon oils such as polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes, propylene isobutylene copolymers, etc.); polyalphaolefins such as poly(1-hexenes), poly-(1-octenes), poly(1-decenes), etc. and mixtures thereof, alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, di-nonylbenzenes, di-(2-ethylhexyl)benzenes, etc.); polyphenyls (e.g., biphenyls, terphenyl, alkylated polyphenyls, etc.); alkylated diphenyl ethers and alkylated diphenyl sulfides and the derivatives, analogs and homologs thereof and the like.

In one embodiment, the synthetic oil for use in the power transmission fluid is selected from the group of alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc. Examples include oils prepared through polymerization of ethylene oxide or propylene oxide, the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g., methylpolyisopropylene glycol ether having an average molecular weight of about 1000, diphenyl ether of polyethylene glycol having a molecular weight of about 500-1000, diethyl ether of polypropylene glycol having a molecular weight of about 1000-1500, etc.) or mono- and polycarboxylic esters thereof, for example, the acetic acid esters, mixed C₃₋₈ fatty acid esters, or the C₁₃ Oxo acid diester of tetraethylene glycol.

In another embodiment, the synthetic oil is selected from esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids, alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acids, alkenyl malonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol, etc.). Examples include dibutyl adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid and the like. Examples of esters useful as synthetic oils also include those made from C₅ to C₁₂ monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylol propane, pentaerythritol, dipentaerythritol, tripentaerythritol, etc.

In one embodiment, the base oil is a poly-alpha-olefin (PAO). Typically, the poly-alpha-olefins are derived from monomers having from about 4 to about 30, or from about 4 to about 20, or from about 6 to about 16 carbon atoms. Examples of useful PAOs include those derived from octene, decene, mixtures thereof, and the like, e.g., 4 cSt at 100° C. poly-alpha-olefins, 6 cSt at 100° C. poly-alpha-olefins, and mixtures thereof. In another embodiment, the base oil comprises mixtures of mineral oil with the foregoing poly-alpha-olefins.

In one embodiment, the base oil or blends thereof comprises at least an isomerized base oil which the product itself, its fraction, or feed originates from or is produced at some stage by isomerization of a waxy feed from a Fischer-Tropsch process (“Fischer-Tropsch derived base oils”). In another embodiment, the base oil comprises at least an isomerized base oil made from a substantially paraffinic wax feed (“waxy feed”).

Fischer-Tropsch derived base oils are disclosed in a number of patent publications, including for example U.S. Pat. Nos. 6,080,301, 6,090,989, and 6,165,949, and US Patent Publication No. US2004/0079678A1, US20050133409, US20060289337. The Fischer-Tropsch process is a catalyzed chemical reaction in which carbon monoxide and hydrogen are converted into liquid hydrocarbons of various forms including a light reaction product and a waxy reaction product, with both being substantially paraffinic.

In one embodiment the isomerized base oil has consecutive numbers of carbon atoms and has less than 25 wt % naphthenic carbon by n-d-M with normalization. In another embodiment, the amount of naphthenic carbon is less than 10 wt. %. In yet another embodiment the isomerized base oil made from a waxy feed has a kinematic viscosity at 100° C. between 1.5 and 3.5 mm²/s.

In one embodiment, the isomerized base oil is made by a process in which the hydroisomerization dewaxing is performed at conditions sufficient for the base oil to have: a) a weight percent of all molecules with at least one aromatic functionality less than 0.30; b) a weight percent of all molecules with at least one cycloparaffinic functionality greater than 10; c) a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 20 and d) a viscosity index greater than 28×Ln (Kinematic viscosity at 100° C.) +80.

In another embodiment, the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized using a shape selective intermediate pore size molecular sieve comprising a noble metal hydrogenation component, and under conditions of 600-750° F. (315-399° C.) In the process, the conditions for hydroisomerization are controlled such that the conversion of the compounds boiling above 700° F. (371° C.) in the wax feed to compounds boiling below 700° F. (371° C.) is maintained between 10 wt % and 50 wt %. A resulting isomerized base oil has a kinematic viscosity of between 1.0 and 3.5 mm²/s at 100° C. and a Noack volatility of less than 50 weight %. The base oil comprises greater than 3 weight % molecules with cycloparaffinic functionality and less than 0.30 weight percent aromatics.

In one embodiment the isomerized base oil has a Noack volatility less than an amount calculated by the following equation: 1000×(Kinematic Viscosity at 100° C.)^(−2.7). In another embodiment, the isomerized base oil has a Noack volatility less than an amount calculated by the following equation: 900×(Kinematic Vicosity at 100° C.)^(−2.8). In a third embodiment, the isomerized base oil has a Kinematic Viscosity at 100° C. of >1.808 mm²/s and a Noack volatility less than an amount calculated by the following equation: 1.286+20 (kv100)^(−1.5)+551.8 e^(−kv100), where kv100 is the kinematic viscosity at 100° C. In a fourth embodiment, the isomerized base oil has a kinematic viscosity at 100° C. of less than 4.0 mm²/s, and a wt % Noack volatility between 0 and 100. In a fifth embodiment, the isomerized base oil has a kinematic viscosity between 1.5 and 4.0 mm²/s and a Noack volatility less than the Noack volatility calculated by the following equation: 160-40 (Kinematic Viscosity at 100° C.).

In one embodiment, the isomerized base oil has a kinematic viscosity at 100° C. in the range of 2.4 and 3.8 mm²/s and a Noack volatility less than an amount defined by the equation: 900×(Kinematic Viscosity at 100° C.)^(−2.8)−15). For kinematic viscosities in the range of 2.4 and 3.8 mm²/s, the equation: 900×(Kinematic Viscosity at 100° C.)^(−2.8)−15) provides a lower Noack volatility than the equation: 160-40 (Kinematic Viscosity at 100° C.)

In one embodiment, the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized under conditions for the base oil to have a kinematic viscosity at 100° C. of 3.6 to 4.2 mm²/s, a viscosity index of greater than 130, a wt % Noack volatility less than 12, a pour point of less than −9° C.

In one embodiment, the isomerized base oil has an aniline point, in degrees F, greater than 200 and less than or equal to an amount defined by the equation: 36×Ln(Kinematic Viscosity at 100° C., in mm²/s)+200.

In one embodiment, the isomerized base oil has an auto-ignition temperature (AIT) greater than the AIT defined by the equation: AIT in ° C.=1.6×(Kinematic Viscosity at 40° C., in mm²/s)+300. In a second embodiment, the base oil as an AIT of greater than 329° C. and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C., in mm²/s)+100.

In one embodiment, the isomerized base oil has a relatively low traction coefficient, specifically, its traction coefficient is less than an amount calculated by the equation: traction coefficient=0.009×Ln (kinematic viscosity in mm²/s)−0.001, wherein the kinematic viscosity in the equation is the kinematic viscosity during the traction coefficient measurement and is between 2 and 50 mm²/s. In one embodiment, the isomerized base oil has a traction coefficient of less than 0.023 (or less than 0.021) when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40%. In another embodiment the isomerized base oil has a traction coefficient of less than 0.017 when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40%. In another embodiment the isomerized base oil has a viscosity index greater than 150 and a traction coefficient less than 0.015 when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40 percent.

In some embodiments, the isomerized base oil having low traction coefficients also displays a higher kinematic viscosity and higher boiling points. In one embodiment, the base oil has a traction coefficient less than 0.015, and a 50 wt % boiling point greater than 565° C. (1050° F.). In another embodiment, the base oil has a traction coefficient less than 0.011 and a 50 wt % boiling point by ASTM D 6352-04 greater than 582° C. (1080° F.).

In some embodiments, the isomerized base oil having low traction coefficients also displays unique branching properties by NMR, including a branching index less than or equal to 23.4, a branching proximity greater than or equal to 22.0, and a Free Carbon Index between 9 and 30. In one embodiment, the base oil has at least 4 wt % naphthenic carbon, in another embodiment, at least 5 wt % naphthenic carbon by n-d-M analysis by ASTM D 3238-95 (Reapproved 2005) with normalization.

In one embodiment, the isomerized base oil is produced in a process wherein the intermediate oil isomerate comprises paraffinic hydrocarbon components, and in which the extent of branching is less than 7 alkyl branches per 100 carbons, and wherein the base oil comprises paraffinic hydrocarbon components in which the extent of branching is less than 8 alkyl branches per 100 carbons and less than 20 wt % of the alkyl branches are at the 2 position. In one embodiment, the FT base oil has a pour point of less than −8° C.; a kinematic viscosity at 100° C. of at least 3.2 mm²/s; and a viscosity index greater than a viscosity index calculated by the equation of =22×Ln (kinematic viscosity at 100° C.)+132.

In one embodiment, the base oil comprises greater than 10 wt. % and less than 70 wt. % total molecules with cycloparaffinic functionality, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 15.

In one embodiment, the isomerized base oil has an average molecular weight between 600 and 1100, and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms. In another embodiment, the isomerized base oil has a kinematic viscosity between about 8 and about 25 mm²/s and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms.

In one embodiment, the isomerized base oil is obtained from a process in which the highly paraffinic wax is hydroisomerized at a hydrogen to feed ratio from 712.4 to 3562 liter H₂/liter oil, for the base oil to have a total weight percent of molecules with cycloparaffinic functionality of greater than 10, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality of greater than 15. In another embodiment, the base oil has a viscosity index greater than an amount defined by the equation: 28×Ln (Kinematic viscosity at 100° C.)+95. In a third embodiment, the base oil comprises a weight percent aromatics less than 0.30; a weight percent of molecules with cycloparaffinic functionality greater than 10; a ratio of weight percent of molecules with monocycloparaffinic functionality to weight percent of molecules with multicycloparaffinic functionality greater than 20; and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C.)+110. In a fourth embodiment, the base oil further has a kinematic viscosity at 100° C. greater than 6 mm²/s. In a fifth embodiment, the base oil has a weight percent aromatics less than 0.05 and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C.)+95. In a sixth embodiment, the base oil has a weight percent aromatics less than 0.30, a weight percent molecules with cycloparaffinic functionality greater than the kinematic viscosity at 100° C., in mm²/s, multiplied by three, and a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality greater than 15.

In one embodiment, the isomerized base oil contains between 2 and 10 wt % naphthenic carbon as measured by n-d-M. In one embodiment, the base oil has a kinematic viscosity of 1.5-3.0 mm²/s at 100° C. and 2-3 wt % naphthenic carbon. In another embodiment, a kinematic viscosity of 1.8-3.5 mm²/s at 100° C. and 2.5-4 wt % naphthenic carbon. In a third embodiment, a kinematic viscosity of 3-6 mm²/s at 100° C. and 2.7-5 wt % naphthenic carbon. In a fourth embodiment, a kinematic viscosity of 10-30 mm²/s at 100° C. and between greater than 5.2 % and less than 25 wt % naphthenic carbon.

In one embodiment, the isomerized base oil has an average molecular weight greater than 475; a viscosity index greater than 140, and a weight percent olefins less than 10. The base oil improves the air release and low foaming characteristics of the mixture when incorporated into the power transmission fluid composition.

Unrefined, refined and rerefined oils, either natural or synthetic (as well as mixtures of two or more of any of these) of the type disclosed hereinabove can be used in the base oil. Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment.

In one embodiment, the power transmission fluid composition employs a base oil that consists of at least one of the isomerized base oils described above. In another embodiment, the composition consists essentially of at least a Fischer-Tropsch base oil. In yet another embodiment, the composition employs at least a Fischer-Tropsch base oil and optionally 5 to 95 wt. % of at least another type of oil, e.g., conventionally used mineral oils, synthetic hydrocarbon oils or synthetic ester oils, or mixtures thereof depending on the application.

In one embodiment, the isomerized base oil is a FT base oil having a kinematic viscosity at 100° C. between 3 cSt and 5 cSt; a kinematic viscosity at 40° C. between 10 cSt and 20 cSt; a viscosity index between 135 and 150; cold cranking viscosity in the range of 1,500-3,500 at −40° C., 1,000-2,000 at −35° C.; pour point in the range of −20 and −30° C.; molecular weight of 400-500; density in the range of 0.805 to 0.820; paraffinic carbon in the range of 94-97 %; naphthenic carbon in the range of 3-6%; oxidator BN of 35 to 50 hours; bromine index of 18 to 28; and TGA Noack in wt. % of 10 to 20 as measured by ASTM D5800-05 Procedure B.

Pour Point Reducing Blend Component: The power transmission fluid composition further comprises a sufficient amount of at least a Pour Point Reducing Blend Component for the Brookfield viscosity at −40° C. to be less than or equal to 16,000 cP. In a second embodiment, the composition further comprises a sufficient amount of at least a Pour Point Reducing Blend Component for the Brookfield viscosity at −40° C. to be less than or equal to 13,000 cP. The amount added depends on the base oil(s) used in the power transmission fluid to be blended.

In one embodiment, this sufficient amount of Pour Point Reducing Blend Component is between 0.5 to 15 wt. %. In a second embodiment, this sufficient amount is between 0.5 to 10 wt. %. In a third embodiment, this amount is less than 8 wt. %. In a fourth embodiment, from 2 to 6 wt. %.

In one embodiment, the Pour Point Reducing Blend Component is an isomerized Fischer-Tropsch derived vacuum distillation bottoms product, which is a high boiling syncrude fraction which has been isomerized under controlled conditions to give a specified degree of alkyl branching in the molecule. Syncrude prepared from the Fischer-Tropsch process comprises a mixture of various solid, liquid, and gaseous hydrocarbons. When the Fischer-Tropsch waxes are converted into Fischer-Tropsch base oils by various processes, such as by hydroprocessing and distillation, the base oils produced fall into different narrow-cut viscosity ranges. The bottoms that remains after recovering the lubricating base oil cuts from the vacuum column is generally unsuitable for use as a lubricating base oil itself and is usually recycled to a hydrocracking unit for conversion to lower molecular weight products.

In one embodiment, the Pour Point Reducing Blend Component is an isomerized Fischer-Tropsch derived vacuum distillation bottoms product having an average molecular weight between 600 and 1 100 and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms. Generally, the higher molecular weight hydrocarbons are more effective as Pour Point Reducing Blend Component s than the lower molecular weight hydrocarbons. In one embodiment, a higher cut point in a vacuum distillation unit which results in a higher boiling bottoms material is used to prepare the Pour Point Reducing Blend Component. The higher cut point also has the advantage of resulting in a higher yield of the distillate base oil fractions. In one embodiment, the Pour Point Reducing Blend Component is an isomerized Fischer-Tropsch derived vacuum distillation bottoms product having a pour point that is at least 3° C. higher than the pour point of the distillate base oil it is blended with.

In one embodiment, the 10 percent point of the boiling range of the Pour Point Reducing Blend Component that is a vacuum distillation bottoms product is between about 850° F.-1050° F. (454-565° C.). In another embodiment, the Pour Point Reducing Blend Component is derived from either Fischer-Tropsch or petroleum products, having a boiling range above 950° F. (510° C.), and contains at least 50 percent by weight of paraffins. In yet another embodiment the pour point reducing blend component has a boiling range above 1050° F. (565° C.)

In another embodiment, the Pour Point Reducing Blend Component is an isomerized petroleum derived base oil containing material having a boiling range above about 1050° F. In one embodiment, the isomerized bottoms material is solvent dewaxed prior to being used as a pour point reducing blend component. The waxy product further separated during solvent dewaxing from the pour point reducing blend component were found to display excellent improved pour point depressing properties compared to the oily product recovered after the solvent dewaxing.

In one embodiment, the Pour Point Reducing Blend Component has an average degree of branching in the molecules within the range of from 6.5 to 10 alkyl branches per 100 carbon atoms. In another embodiment, the Pour Point Reducing Blend Component has an average molecular weight between 600-1 100. In a third embodiment, between 700-1000. In one embodiment, the Pour Point Reducing Blend Component has a kinematic viscosity at 100° C. of 8-30 mm²/s, with the 10% point of the boiling range of the bottoms falling between about 850-1050° F. In yet another embodiment, the Pour Point Reducing Blend Component has a kinematic viscosity at 100° C. of 15-20 mm²/s and a pour point of −8 to −12° C.

In another embodiment, the Pour Point Reducing Blend Component is an isomerized oil having a kinematic viscosity at 100° C. of at least about 8 mm²/s made from polyethylene plastic. In another embodiment, the Pour Point Reducing Blend Component is made from waste plastic. In yet another embodiment the Pour Point Reducing Blend Component is made from a process comprising: pyrolysis of polyethylene plastic, separating out a heavy fraction, hydrotreating the heavy fraction, catalytic isomerizing the hydrotreated heavy fraction, and collecting the Pour Point Reducing Blend Component having a kinematic viscosity at 100° C. of at least about 8 mm²/s. In one embodiment, the Pour Point Reducing Blend Component derived from polyethylene plastic has a boiling range above 1050° F. (565° C.), or even a boiling range above 1200° F. (649° C.).

In one embodiment, besides the Pour Point Reducing Blend Component, other commercially available pour point depressant additives can also be added in an amount from 0.5 to 10 wt. % to usefully optimize the low temperature fluidity of the composition. Examples include C₈-C₁₈ dialkylfumarate vinyl acetate copolymers, wax naphthalene condensation products, maleic anhydride-styrene copolymers, polymethacrylates, polyacrylates, polyacrylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids, ethylene-vinyl acetate copolymers, alkyl phenol formaldehyde condensation resins, alkyl vinyl ethers, olefin copolymers, and mixtures thereof.

Additional Components: In one embodiment, the power transmission fluid contains additives such as viscosity index improvers, friction modifiers, corrosion inhibitors, oxidation inhibitors, friction modifiers, demulsifiers, anti foamant, anti wear agents, pour point depressants, seal swellants, dyes, markers, biocides, antistatic additives, drag-reducing agents, demulsifiers, dehazers, anti-icing additives, anti-knock additives, anti-valve-seat recession additives, lubricity additives, combustion improvers, cold flow improvers, antirust additives, metal deactivators, air expulsion additives, and other additives known in the art. Some of these additives can provide a multiplicity of effects, e.g., a dispersant-oxidation inhibitor.

In one embodiment, the additional component is a viscosity index (VI) improver in an amount of 1 to 15 wt. %. of the final weight of the power transmission fluid. In yet another embodiment, the VI improver(s), whether present individually or in combination, are present in sufficient amounts so that the transmission fluid composition has the viscometric properties of one or more of the sets of specified viscometric performance. Examples of viscosity index improvers include poly alkyl(meth)acrylates of low Brookfield viscosity and high shear stability, functionalized poly alkyl(meth)acrylates with dispersant properties of high Brookfield viscosity and high shear stability, polyisobutylene having a weight average molecular weight ranging from 700 to 2,500, and mixtures thereof. In one embodiment, the first poly alkyl (meth) acrylate having a weight average molecular weight of about 125,000 to 225,000, a shear stability index of 15 or less, a Brookfield viscosity at −40° C. of between about 200,000 to 600,000 cP. In one embodiment, the second poly alkyl(meth)acrylate viscosity index improver has a weight average molecular weight in the range 50,000 to 150,000, a shear stability index of about 10 or less, and a Brookfield viscosity at −40° C. of between about 10,000 to 30,000 cP.

In one embodiment, the viscosity index improver is a graft copolymer comprising a polymer backbone which has been grafted by reacting the polymer backbone with a reactant comprising N-p-diphenylamine, 1,2,3,6-tetrahydrophthalimide; 4-anilinophenyl methacrylamide; 4-anilinophenyl maleimide; 4-anilinophenyl itaconamide; an acrylate or methacrylate ester of 4-hydroxydiphenylamine; a reaction product of p-aminodiphenylamine or p-alkylaminodiphenylamine with glycidyl methacrylate; a reaction product of p-aminodiphenylamine with isobutyraldehyde, a derivative of p-hydroxydiphenylamine; a derivative of phenothiazine; a vinylogous derivative of diphenylamine.

In one embodiment, the additives are incorporated as a “performance additive package.” As used herein, the term “performance additive package” means any combination of additives listed above for power transmission fluid compositions. In one embodiment, the performance additive package is a commercially available package, added in an amount from about 1% to about 15% by weight of the finished composition.

In one embodiment, the power transmission fluid comprises a performance additive package designed for improved friction durability, comprising a borated dispersant, a succinimide, and a phosphorus-containing antiwear component. In one example, the succinimide is prepared from an alkenyl succinic acid or anhydride and ammonia. The phosphorus-containing antiwear component may consist essentially of an organic ester of phosphoric acid or phosphorous acid.

In another embodiment, the performance additive package is a commercially available manual transmission fluid additive package, added in an amount from about 1% to about 10% of the weight of the finished power transmission fluid composition. An example of a package is Infineum T4804 from Infineum, which contains anti-foamant, antioxidant, rust inhibitor, magnesium sulfonate detergent, seal swellant, amine phosphate antiwear additive, borated polyisobutenyl succinimide dispersant and friction modifier, each present in customary amounts so as to provide their normal attendant function.

In a third embodiment, the performance additive package is an automatic transmission fluid (ATF) additive package, which comprises from about 1 to about 20% of the weight of the finished power transmission fluid composition. An ATF additive package typically consists of ashless dispersants; anti-wear agents; anti-oxidants; corrosion inhibitors; friction modifiers; seal swell agents; anti-foamants and sometimes viscosity modifiers. Examples of commercially available automatic transmission fluid additives include but are not limited to: Lubrizol 6950; Lubrizol 7900; Lubrizol 9614 from the Lubrizol Corporation; Hitec 403; Hitec 420; Hitec 427 from the Ethyl Corporation and Infineum T4520, Infineum T4540 from Infineum.

In one embodiment and instead of/in addition to a commercially available performance additive package, the power transmission fluid composition further comprises at least a friction modifier. In one embodiment, the friction modifier is selected from the group of succinamic acid, succinimide, and mixtures thereof. In another embodiment, the friction modifier is selected from an aliphatic fatty amine, an ether amine, an alkoxylated aliphatic fatty amine, an alkoxylated ether amine, an oil-soluble aliphatic carboxylic acid, a polyol ester, a fatty acid amide, an imidazoline, a tertiary amine, a hydrocarbyl succinic anhydride or acid reacted with an ammonia or a primary amine, and mixtures thereof.

Corrosion inhibitors, also known as anti-corrosive agents, can be added to reduce the degradation of the metallic parts contained in the power transmission fluid. Illustrative of corrosion inhibitors are zinc dialkyldithiophosphate, phosphosulfurized hydrocarbons and the products obtained by reaction of a phosphosulfurized hydrocarbon with an alkaline earth metal oxide or hydroxide, preferably in the presence of an alkylated phenol or of an alkylphenol thioester, and also preferably in the presence of carbon dioxide. Phosphosulfurized hydrocarbons are prepared by reacting a suitable hydrocarbon such as a terpene, a heavy petroleum fraction of a C₂ to C₆ olefin polymer such as polyisobutylene, with from 5 to 30 wt % of a sulfide of phosphorous for ½ to 15 hours, at a temperature in the range of 150° F. to 600° F.

Metal detergents can also be added to the power transmission fluid composition, including a detergent selected from one or more of a neutral sodium sulfonate, an overbased sodium sulfonate, a sodium carboxylate, a sodium salicylate, a sodium phenate, a sulfurized sodium phenate, a lithium sulfonate, a lithium carboxylate, a lithium salicylate, a lithium phenate, a sulfurized lithium phenate, a magnesium sulfonate, a magnesium carboxylate, a magnesium salicylate, a magnesium phenate, a sulfurized magnesium phenate, a potassium sulfonate, a potassium carboxylate, a potassium salicylate, a potassium phenate, a sulfurized potassium phenate, a zinc sulfonate, a zinc carboxylate, a zinc salicylate, a zinc phenate, and a sulfurized zinc phenate.

Oxidation inhibitors/antioxidants can be added to reduce the tendency of the base oils in the power transmission fluid to deteriorate in service, which deterioration is evidenced by the products of oxidation such as sludge and varnish-like deposits on the metal surfaces. Examples include phenyl naphthyl amines, see U.S. Pat. No. 3,414,618; compounds such as phenylene diamine, phenothiazine, diphenyl amine, diarylamine. In one embodiment, antioxidants are selected from phenyl-alphanaphthylamine, 2,2′-diethyl-4,4′-dioctyl diphenylamine, 2,2′diethyl-4-t-octyldiphenylamine, and mixtures thereof; which antioxidants further function as corrosion inhibitors. Other suitable antioxidants which also function as antiwear agents include bis alkyl dithiothiadiazoles such as 2,5-bis-octyl dithiothiadiazole. In another embodiment, oxidation inhibitors are used, including alkaline earth metal salts of alkylphenol thioesters, having C₅ to C₁₂ alkyl side chains, e.g., calcium nonylphenol sulfide, barium t-octylphenol sulfide, zinc dialkylditbiophosphates, dioctylphenylamine, phenylalphanaphthylamine, phosphosulfurized or sulfurized hydrocarbons, etc.

Dispersants maintain oil insolubles, resulting from oxidation during use, can be added in suspension in power transmission fluids, thus preventing sludge flocculation and precipitation. Suitable dispersants include succinimide dispersant derived from a polyisobutenyl succinic anhydride (PIBSA), high molecular weight alkyl succinates, the reaction product of oil-soluble polyisobutylene succinic anhydride with ethylene amines such as tetraethylene pentamine and borated salts thereof.

In one embodiment, the power transmission fluid further comprises an anti-foamant of the polysiloxane type, e.g., silicone oil and polydimethyl siloxane, for foam control. In another embodiment, the anti-foamant is a mixture of polydimethyl siloxane and flurosilicone. In yet another embodiment, the power transmission fluid further comprises an acrylate polymer anti-foamant, with a weight ratio of the fluorosilicone antifoamant to the acrylate anti-foamant ranging from about 3:1 to about 1:4. In a fourth embodiment, the power transmission fluid comprises an anti-foam-effective amount of a silicon-containing anti-foamant such that the total amount of silicon in the power transmission fluid is at least 30 ppm to reduce or eliminate the whining noise that may occur in high-pressure pumps used to circulate transmission fluids in vehicles. In one embodiment, the silicon-containing antifoam agent is selected from the group consisting of fluorosilicones, polydimethylsiloxane, phenyl-methyl polysiloxane, linear siloxanes, cyclic siloxanes, branched siloxanes, silicone polymers and copolymers, organo-silicone copolymers, and mixtures thereof.

Anti-wear agents can also be added to reduce wear of transmission parts. Representative of suitable antiwear agents are zinc dialkyldithiophosphate, zinc diaryldilhiophosphate and magnesium sulfonate.

In one embodiment, the composition further comprises seal swellants include mineral oils of the type that provoke swelling and aliphatic alcohols of 8 to 13 carbon atoms such as tridecyl alcohol, with a preferred seal swellant being characterized as an oil-soluble, saturated, aliphatic or aromatic hydrocarbon ester of from 10 to 60 carbon atoms and 2 to 4 ester linkages, e.g., dihexylphthalate, as are described in U.S. Pat. No. 3,974,081.

Method for Making: Additives used in formulating the compositions can be blended into the base oil matrix individually or in various sub-combinations. In one embodiment, all of the components are blended concurrently using an additive concentrate (i.e., additives plus a diluent, such as a hydrocarbon solvent). The use of an additive concentrate takes advantage of the mutual compatibility afforded by the combination of ingredients when in the form of an additive concentrate. In another embodiment, the power transmission fluid composition is prepared by mixing the base oil and the pour point depressant with the separate additives or additive package(s) at an appropriate temperature, e.g., 60° C., until homogeneous.

Applications: The power transmission fluid composition serves a multitude of purposes and for a number of power transmitting applications including but not limited to mobile and/or stationary applications, e.g., automatic transmissions, manual transmissions, dual clutch transmissions, continuously variable transmissions, automated manual transmissions, transfer cases, axles and differentials in automotive and commercial vehicle services. In one embodiment, it is used to lubricate one or more of a slipping torque converter, a lock-up torque converter, a starting clutch, and one or more shifting clutches. In another embodiment, it is for use in a belt, chain, or disk-type continuously variable transmission.

Among other things, power transmission fluid composition cleans, cools, lubricates, transmits force, transmits pressure, inhibits varnish build-up and protects the transmission of automotive and commercial vehicles on a day-to-day basis.

Properties: Viscometrics is an important lubricant parameter that governs the successful operation of the transmission. In one embodiment, the power transmission fluid composition has an excellent Brookfield viscosity with its base oil blend comprising the Pour Point Reducing Blend Component. The blend gives a Brookfield viscosity lower than the arithmetic mean one would have expected from simply blending of the materials in the base stock, permitting a wider range of more readily available and cheaper base oil materials to achieve a desired result. In one embodiment, the composition has a Brookfield viscosity at 40° C. of 20,000 cp or less. In a second embodiment, a Brookfield viscosity at 40° C. of 16,000 cp or less. In a third embodiment, a Brookfield viscosity at 40° C. of 13,000 cp or less.

In one embodiment, the power transmission fluid composition has a kinematic viscosity at 100° C. between 5 and 9. In a second embodiment, a kinematic viscosity at 100° C. between 6 and 8. In a third embodiment, a kinematic viscosity at 100° C. between 6.5 and 7.5.

Low temperature characteristics and shear stability requirements are becoming more important in power transmission fluids. In one embodiment, the composition has a high shear stability, with the shear stability index of about 30 or less. In a second embodiment, the power transmission fluid composition has a shear stability index of about 20 or less. In a third embodiment, about 10 or less. Shear stability can be expressed by a shear stability index (SSI), which is a measure of the tendency of power transmission fluid compositions to degrade and lose their ability to thicken and maintain viscosity, when subjected to shearing. Shearing can occur in pumps, gears, engines, etc. SSI can be measured by the Sonic Shear Method as set forth in ASTM Test D-5621, per equation below: SSI=(μ_(i)−μ_(f))*100/(μ_(i)−μ_(o)), wherein μ_(i) is the initial viscosity of the fresh, unsheared ATF in cSt at 100° C., μ_(f) is the final viscosity of the power transmission fluid after test in cSt at 100° C., and μ_(o) is the viscosity in cSt at 100° C. of the power transmission fluid base mixture with all additives except the viscosity index improvers.

In one embodiment with the use of advanced additive package, e.g., a package having detergent-inhibitor and shear-stable viscosity index improver in the range of 10 to 15 wt. %., the power transmission fluid exhibits excellent service life of up to 150,000 miles in passenger cars and trucks before a necessary drain interval. Furthermore, the power transmission fluid maintains its viscosity with less than or equal to 5% viscosity over the life of the fluid.

The following Examples are given as non-limitative illustration of aspects of the invention.

EXAMPLES

Unless specified otherwise, the components in the examples are as follows:

FTBO base oils (FTBO-1 to FTBO-4) are from Chevron Corporation of San Ramon, Calif. The properties of the FTBO base oils used in the examples are shown in Table 1.

Fischer-Tropsch derived bottoms—FTBO-5: also from Chevron Corporation, with the properties are as listed in Table 1.

Group III plus base stock is a commercially available base oil.

Infineum IDN3190 is an additive package from Infineum USA LLC.

Viscoplex 1-300 is a polyalkylmethacrylate additive from Rohm & Haas GmbH.

Unless specified otherwise, the components as listed in Table 2 were blended together to form Examples 1-11 and their properties were measured. The results are also shown in Table 2. As shown, the addition of a sufficient amount of a Pour Point Reducing Blend Component with a kinematic viscosity at 100° C. of 16.24 cSt and a pour point of −10° C., lowered the Brookfield viscosity of the power transmission fluids in various embodiments from ⅓ to ½ the Brookfield viscosity of samples without the pour point depressant.

TABLE 1 FTBO 1 FTBO 2 FTBO 3 FTBO 4 FTBO 5 Properties Kinematic viscosity @40° C., cSt 16.74 16.94 13.79 18.13 108.4 Kinematic viscosity @100° C., cSt 3.994 4.058 3.562 4.271 16.24 Viscosity Index 140 144 146 147 161 Cold Crank Viscosity @−40° C., cP 2,449 2,579 1,700 3,058 Cold Crank Viscosity @−35° C., cP 1,470 1,552 1,167 1,761 Cold Crank Viscosity @−30° C., cP 907 1,005 45,916 Cold Crank Viscosity @−25° C., cP 17,874 Cold Crank Viscosity @−20° C., cP 8,276 Pour Point, ° C. −29 −24 −27 −22 −10 n-d-m Molecular Weight, gm/mol (VPO) 429 429 413 434 778 Density, gm/ml 0.8125 0.8125 0.8089 0.8135 0.8328 Refractive Index 1.4534 1.4537 1.4519 1.4541 1.4639 Paraffinic Carbon, % 95.82 95.26 96.32 94.66 93.19 Naphthenic Carbon, % 4.18 4.74 3.68 5.34 6.81 Aromatic Carbon, % 0.00 0.00 0.00 0.00 0.00 Oxidator BN, hrs 42.04 36.35 — 37.17 46.08 Noack, wt. % 13.42 7.86 18.69 9.32 0.98 HPLC-UV (LUBES) Aromatics Total 0.01491 0.01147 0.0353 0.00283 0.0325 COC Flash Point, ° C. SIMDIST TBP (WT %), F. TBP @0.5 702 687 327 714 910 TBP @5 731 727 609 749 963 TBP @10 743 740 733 763 991 TBP @20 760 758 760 780 1015 TBP @30 775 774 776 795 1044 TBP @40 790 791 789 808 1063 TBP @50 805 808 801 822 1081 TBP @60 820 826 814 837 1100 TBP @70 836 845 826 852 1122 TBP @80 854 865 840 869 1151 TBP @90 873 888 855 886 1193 TBP @95 886 901 866 896 1230 TBP @99.5 908 922 893 912 1313 FIMS Saturates 79 79.6 81.1 79.5 59.9 1-Unsaturation 19.4 19.3 17.9 19.2 35.6 2-Unsaturation 1.4 1 0.8 1.3 1.3 3-Unsaturation 0.1 0.1 0.1 0 0 4-Unsaturation 0.1 0 0 0 0 5-Unsaturation 0 0 0 0 0 6-Unsaturation 0 0 0.1 0 0 MW 429 429 413 434 778 Number of Carbons 30.64 30.64 29.50 31.00 55.57 Branching Index 27.03 26.95 27.25 26.46 20.28 Branching Proximity 15.80 17.73 17.55 18.83 27.15 Alkyl Branches per Molecule 2.86 2.86 2.71 2.89 4.23 Methyl Branches per Molecule 2.31 2.36 2.26 2.39 3.47 % Olefins by Proton NMR 0.00 0.00 0.00 0.00 0.00 Wt. % molecules with 19.4 19.3 17.9 19.2 35.6 Monocycloparaffin functionality Wt. % molecules with 1.6 1.1 1.0 1.3 1.3 Multicycloparaffin functionality Mono/Multi ratio 12.2 17.7 18.6 14.8 28.1

TABLE 2 Pour point Vis @ Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Component wt. % ° C. 100° C. Wt. % Wt. % Wt. % Wt. % Wt. % Wt. % FTBO 1 −22 4.271 79.0 — — — — 45.0 FTBO 2 −24 4.058 — 79.0 78.8 — — — FTBO 3 −29 3.994 — — — 31.6 4.0 — FTBO 4 −27 3.562 — — — 45.0 70.3 34.0 Pour point FTBO 5 −10 16.24 — — — 2.4 4.7 — Group III −23 4.065 — — — — — — IDN3190 11.0 11.0 11.0 11.0 11.0 11.0 Viscoplex 12-115 10.0 10.0 10.0 10.0 10.0 10.0 Viscoplex 1-300 0.2 — — — 100.0 100.0 100.0 100.0 100.0 100.0 Vis @ 40° C., cSt 18.13 16.94 15.91 15.84 16.38 Vis @ 100° C., cSt 4.271 4.058 3.930 3.942 4.022 Viscosity Index 147 144 149 151 150 Pour Point, ° C. −22 −24 −28 −27 −19 Cloud Point, ° C. −13 −13 −11 −8 −12 Viscosity, cSt, 40° C. 32.86 30.63 31.12 28.79 28.71 29.49 Viscosity, cSt, 100° C. 7.413 7.085 7.165 6.784 6.842 6.928 Viscosity Index 202 206 205 207 212 209 Brookfield vis, cP @ −40° C. 34,150 23,850 34,850 10,020 8,610 24,250 Appearance C&B C&B C&B C&B C&B C&B Pour Point, C. −42 −43 −42 −44 −44 −42 Cloud Point, C. −15 −16 −19 −15 −12 −16 Pour point Vis @ Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Component wt. % ° C. 100° C. Wt. % Wt. % Wt. % Wt. % Wt. % FTBO 1 −22 4.271 9.5 20.8 — — — FTBO 2 −24 4.058 — — — — — FTBO 3 −29 3.994 — — — — — FTBO 4 −27 3.562 64.8 53.5 71.1 71.1 — Pour point FTBO 5 −10 16.24 4.7 4.7 7.9 7.9 — Group III −23 4.065 — — — — 79.0 IDN3190 11.0 11.0 11.0 11.0 11.0 Viscoplex 12-115 10.0 10.0 10.0 10.0 10.0 Viscoplex 1-300 — — — — — 100.0 100.0 100.0 100.0 100.0 Vis @ 40° C., cSt 16.30 19.68 16.87 16.94 17.35 Vis @ 100° C., cSt 4.022 4.159 4.171 4.160 4.065 Viscosity Index 152 155 154 156 138 Pour Point, ° C. −27 −25 −27 −23 Cloud Point, ° C. −9 −7 5 −18 Viscosity, cSt, 40° C. 29.12 30.02 30.17 29.66 31.09 Viscosity, cSt, 100° C. 6.907 7.023 7.095 6.981 7.07 Viscosity Index 211 208 211 210 201 Brookfield vis, cP @ −40° C. 11,120 13,800 16040 21,100 14,200 Appearance C&B C&B C&B C&B C&B Pour Point, C. −44 −44 −46 −43 −44 Cloud Point, C. −11 −11 −9 −8 −22

For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained and/or the precision of an instrument for measuring the value. Furthermore, all ranges disclosed herein are inclusive of the endpoints and are independently combinable. In general, unless otherwise indicated, singular elements may be in the plural and vice versa with no loss of generality. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. All citations referred herein are expressly incorporated herein by reference. 

1. A power transmission fluid composition comprising: (a) a base oil; (b) at least one of an additive package, viscosity index improver, friction modifier, corrosion inhibitor, oxidation inhibitor, friction modifier, demulsifier, anti foamant, anti wear agent, seal swellant, dye, markers, biocide, antistatic additive, drag-reducing agent, demulsifier, dehazer, anti-icing additive, anti-knock additive, anti-valve-seat recession additive, lubricity additive, combustion improver, cold flow improver, antirust additive, metal deactivator, air expulsion additive; and (c) a sufficient amount of a pour point depressant comprising a Pour Point Reducing Blend Component for the power transmission fluid to have a Brookfield viscosity at −40° C. of less than or equal to 16,000 cP, wherein the Pour Point Reducing Blend Component has an average degree of branching within a range of 6.5 to 10 alkyl branches per 100 carbon atoms; and wherein the power transmission fluid has a kinematic viscosity at 100° C. between 5 and9.
 2. The composition of claim 1, wherein the base oil is selected from the group of a natural oil, a synthetic oil, an isomerized base oil, and mixtures thereof.
 3. The composition of claim 2, wherein the base oil is selected from the group of a mineral oil, a vegetable oil, an oligomer of an alphaolefin, an ester, an oil derived from a gas-to-liquid process, a Fischer-Tropsch derived base oil, and mixtures thereof.
 4. The composition of claim 1, wherein the base oil consists essentially of an isomerized base oil having a kinematic viscosity at 100° C. between 3 cSt and 5 cSt, a kinematic viscosity at 40° C. between 10 cSt and 20 cSt, a viscosity index between 135 and 150, a cold cranking viscosity in the range of 1,500-3,500 at -40° C.; a pour point in the range of −20 and −30° C.; a molecular weight of 400-500; and a density in the range of 0.805 to 0.820.
 5. The composition of claim 1, wherein the base oil has a kinematic viscosity of from 2 centistokes to 10 centistokes at 100° C.
 6. The composition of claim 5, wherein the power transmission fluid has a kinematic viscosity at 100° C. between 6.5 and
 7. 7. The composition of claim 1, wherein the power transmission fluid has a shear stability index of 30 or less.
 8. The composition of claim 7, wherein the power transmission fluid has a shear stability index of 20 or less.
 9. The composition of claim 1, wherein the Pour Point Reducing Blend Component is an isomerized Fischer-Tropsch derived bottoms product.
 10. The composition of claim 9, wherein the Pour Point Reducing Blend Component has an average molecular weight between 600-1100.
 11. The composition of claim 9, wherein the Pour Point Reducing Blend Component has a kinematic viscosity at 100° C. of 8-22 cSt, with a 10% point of the boiling range of the Pour Point Reducing Blend Component falling between about 850-1050° F.
 12. The composition of claim 9, wherein the Pour Point Reducing Blend Component has a pour point of −8 to −12° C.
 13. The composition of claim 1, wherein the sufficient amount of a Pour Point Reducing Blend Component for the power transmission fluid to have a Brookfield viscosity at −40° C. of less than or equal to 16,000 cP is between 0.5 to 15 wt. %.
 14. The composition of claim 1, wherein the sufficient amount of a Pour Point Reducing Blend Component is between 0.5 to 10 wt. %.
 15. The composition of claim 1, wherein the sufficient amount of a Pour Point Reducing Blend Component is between 2 to 6 wt. %.
 16. The composition of claim 1, wherein the sufficient amount of a Pour Point Reducing Blend Component for the power transmission fluid is between 2 to 6 wt. %. for the Brookfield viscosity at −40° C. to be less or equal to 13,000 cP.
 17. The composition of claim 1, wherein the composition comprises at least an anti-foamant selected from the group of silicone oils, polydimethyl siloxane, flurosilicone, acrylate polymer, phenyl-methyl polysiloxane, linear siloxanes, cyclic siloxanes, branched siloxanes, silicone polymers, silicone copolymers, organo-silicone copolymers, and mixtures thereof.
 18. The composition of claim 1, wherein the composition comprises at least a viscosity index improver selected from the group of a) poly alkyl(meth)acrylates; b) functionalized poly alkyl(meth)acrylates; c) a polyisobutylene having a weight average molecular weight ranging from 700 to 2,500; d) a graft copolymer comprising a polymer backbone which has been grafted by reacting the polymer backbone with a reactant comprising N-p-diphenylamine, 1,2,3,6-tetrahydrophthalimide; 4-anilinophenyl methacrylamide; 4-anilinophenyl maleimide; 4-anilinophenyl itaconamide; an acrylate or methacrylate ester of 4-hydroxydiphenylamine; a reaction product of p-aminodiphenylamine or p-alkylaminodiphenylamine with glycidyl methacrylate; a reaction product of p-aminodiphenylamine with isobutyraldehyde, a derivative of p-hydroxydiphenylamine; a derivative of phenothiazine; a vinylogous derivative of diphenylamine; and mixtures thereof.
 19. The composition of claim 1, wherein the composition comprises at least a dispersant selected from the group of succinimides derived from a polyisobutenyl succinic anhydride (PIBSA), high molecular weight alkyl succinates, reaction products of oil-soluble polyisobutylene succinic anhydride with ethylene amines, and mixture thereof.
 20. The composition of claim 1, wherein the composition comprises at least a metal detergent selected from: a neutral sodium sulfonate, an overbased sodium sulfonate, a sodium carboxylate, a sodium salicylate, a sodium phenate, a sulfurized sodium phenate, a lithium sulfonate, a lithium carboxylate, a lithium salicylate, a lithium phenate, a sulfurized lithium phenate, a magnesium sulfonate, a magnesium carboxylate, a magnesium salicylate, a magnesium phenate, a sulfurized magnesium phenate, a potassium sulfonate, a potassium carboxylate, a potassium salicylate, a potassium phenate, a sulfurized potassium phenate, a zinc sulfonate, a zinc carboxylate, a zinc salicylate, a zinc phenate, a sulfurized zinc phenate, and mixtures thereof.
 21. The composition of claim 1, wherein the composition comprises at least a friction modifier selected from succinamic acid, succinimide, an aliphatic fatty amine, an ether amine, an alkoxylated aliphatic fatty amine, an alkoxylated ether amine, an oil-soluble aliphatic carboxylic acid, a polyol ester, a fatty acid amide, an imidazoline, a tertiary amine, a hydrocarbyl succinic anhydride or acid reacted with an ammonia or a primary amine, and mixtures thereof
 22. The composition of claim 1, wherein the composition is an automatic transmission fluid.
 23. A method of improving the Brookfield viscosity characteristic of a power transmission fluid including the step of mixing: (a) a base oil; (b) at least one of an additive package, a friction modifier, a dispersant, an antioxidant, an anti-foamant, an antiwear agent, an antifoam agent, a metal-based detergent, and a viscosity index improver; with (c) a sufficient amount of a pour point depressant comprising a Pour Point Reducing Blend Component for the power transmission fluid to have a Brookfield viscosity at −40° C. of less than or equal to 16,000 cP.
 24. The method of claim 23, wherein between 0.5 to 10 wt. %. of the Pour Point Reducing Blend Component is added to the mixture for the power transmission fluid to have a Brookfield viscosity at −40° C. of less than or equal to 16,000 cP.
 25. The method of claim 24, wherein between 0.5 to 6 wt. %. of the Pour Point Reducing Blend Component is added to the mixture for the power transmission fluid to have a Brookfield viscosity at −40° C. of less than or equal to 13,000 cP. 